This invention relates generally to intravenous infusion and, more particularly, to a winged catheter for intravenous infusion which is assembled from a plurality of polyurethane parts and formed into an integral unit by means of dielectric heating using radio frequency energy.
Commonly used intravenous infusion assemblies comprise needle and catheter sets wherein a needle extends within a flexible catheter having so-called "wings" attached to the catheter assembly. For insertion, one grips the wings, squeezing them between the thumb and forefinger, to assist in accurately positioning the catheter sheathed needle into a desired vein.
Once positioned, the needle is removed from the catheter leaving only the flexible catheter in place such that the vein is not likely to be ruptured as a result of minor relative movements between the infusion assembly and the vein. Two varieties of combination needle/catheter sets are shown respectively in U.S. Pat. No. 3,094,122 issued Jan. 18, 1963 to Gauthier et al. and U.S. Pat. No. 4,362,156 issued Dec. 7, 1982 to Feller et al.
It is important that the individual elements forming the infusion assembly be securely bonded together to prevent leakage from the assembly and detachment of the catheter. Many of the solutions passed through an intravenous infusion assembly may cause discomfort or pain if allowed to contact a patient's skin. This is particularly true with many chemotheraputic agents utilized to treat cancer patients. Even if the solution is not toxic, bacterial contamination is a problem once an opening appears in the intravenous infusion assembly. The complications of a detached catheter within a patient's vein are potentially even graver. Accordingly, serious problems can arise if the catheter assembly is not properly manufactured.
A typical infusion assembly comprises a catheter, a winged catheter gripping member, a section of tubing and a fluid receiving hub. In the prior art, a variety of methods have been utilized to interconnect the parts making up such an assembly. The parts have been mechanically interconnected by forcing a conical wedge into the proximal end of the catheter to lock the catheter in the catheter hub. Such mechanical interconnection is often referred to as "staking" or "swedging" and can be expensive and time consuming. Futhermore, the presence of the wedge in the infusion stream creates turbulent flow which can interfere with metering the infusion liquid.
The parts have also been glued together by means of an appropriate adhesive. However, gluing requires a biocompatible adhesive and is typically messy. Gluing also can lead to inadvertent blockage of a portion of the assembly passageway particularly when small gauge catheters are utilized.
Solvent bonding has also been utilized. In solvent bonding, each of the parts is made from a material which is soluble in a particular solvent. When the solvent is applied to the parts and the parts are intermated, dissolved surface portions of the two intermingle with one another to form a bond. Unfortunately, solvent bonding has proved to be only marginally reliable in preventing leakage. Solvent bonding also is expensive and time consuming when used for the assembly of intravenous infusion devices.
One assembly means which has been used in forming a Foley catheter unit is by welding the individual parts together using dielectric heating cuased by radio frequency (RF) energy. However, radio frequency welding or bonding has not been applied in the manufacture of intravenous infusion assemblies. Problems encountered in RF bonding have centered around the frequencies and power levels utilized as well as the formation of the power applying electrodes. For example, if insufficient power is applied to the parts, the welds or bonds are not reliable. On the other hand, excessive power can lead to arcing of the radio frequency energy at the electrodes and may damage the RF power supply and/or cause the small openings of the passageways through the intravenous infusion assembly to be blocked.
Thus, it is apparent that the need exists for an integral catheter intravenous infusion assembly which will provide high reliability against leakage of possibly toxic materials onto a patient's skin as well as detachment of the catheter from the intravenous infusion assembly.